Answer:
D. FBI
Explanation:The Federal Bureau of Investigation, or FBI, and its longtime director, J. Edgar Hoover(1895-1972), aided many of the legislative investigations of communist activities. An ardent anticommunist, Hoover had been a key player in an earlier, though less pervasive, Red Scare in the years following World War I (1914-18). With the dawning of the new anticommunist crusade in the late 1940s, Hoover’s agency compiled extensive files on suspected subversives through the use of wiretaps, surveillance and the infiltration of leftist groups.The information obtained by the FBI proved essential in high-profile legal cases, including the 1949 conviction of 12 prominent leaders of the American Communist Party on charges that they had advocated the overthrow of the government. Moreover, Hoover’s agents helped build the case against Julius Rosenberg (1918-53) and his wife, Ethel Rosenberg (1915-53), who were convicted of espionage in 1951. The Rosenbergs were executed two years later.
